People communicate wirelessly and on the go. Among the devices that make this possible are those sometimes referred to as personal mobile devices. Examples of personal mobile devices include cell phones, smartphones, walkie-talkies, and portable hotspots, among others. A personal mobile device could be handheld (as may be the case for a walkie-talkie), body-mounted, or attached to a vehicle (such as the roof of a car), as examples.
Given the relative ease with which radio signals can be intercepted, communication with (or between) personal mobile devices is often encrypted to prevent interception of the communication by third parties. Encryption is the process of converting audible voice or other data into unintelligible voice, while decryption is the process of converting the unintelligible voice back to the original audible voice. The respective algorithms used for encryption and decryption are often referred to collectively as a cipher. Examples of common ciphers include Advanced Encryption Standard (AES), Blowfish, Triple Data Encryption Algorithm (3DES), and RC4, among numerous others.
A given cipher typically uses one or more cryptographic keys for encryption and decryption. Common examples of cryptographic keys include passwords, digital certificates, and random and/or pseudo-random data. Any party (including a third party) with access to a cryptographic key used to encrypt a given plaintext may be able to decrypt the unintelligible voice; therefore, for encryption to be effective, the cryptographic key should be known only to the sender and receiver. Encryption and decryption may take place in a secure element that is external to the personal mobile device.